This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
This genus includes all the different races of Stocks. Its distinctive characters are : entire or sinuate leaves, large flowers, the petals having long claws, a nearly cylindrical pod, connivent stigmas thickened or horned at the back, and thin flat numerous seeds. About thirty species, chiefly from the Mediterranean region. Named after an Italian physician.
1. M. incana. - This is the sub-shrubby biennial species from which the Brompton and perhaps the Queen Stocks have descended. It is an erect hoary plant, 1 to 3 feet high, with oblong-lanceolate entire leaves and large white, crimson, violet, purple double or single flowers. M. fenestralis, Giant Cape Stock, is referred to this species by some authors. A native of the West of Europe and the Levant, and also found on cliffs in the Isle of Wight.
2. M. annua. - The Ten-week, Intermediate, and other garden annual varieties of Stocks belong to this species. This has produced innumerable varieties, from pure white, lilac, violet, rose, and crimson to purple. Mediterranean region.
3. M. Graeca. The Wallflower-leaved Stock. - The foliage of this, instead of being hoary and downy, is of a bright green, closely resembling that of the Wallflower. This includes some white and yellow annual varieties. South of Europe.
4. M. bicornis. - A straggling annual with lilac flowers, very fragrant at night, but closed during the day. It has a two-horned pod. It flowers during the Summer months. South of Europe.